Aspergillus to Zygomycetes: Causes, Risk Factors, Prevention, and Treatment of Invasive Fungal Infections

Abstract

Invasive fungal infections (IFIs) are an important cause of morbidity and mortality, particularly in patients with underlying risk factors (e.g., neutropenia, cancer chemotherapy, transplantation, AIDS). Although Candida species remain a relevant cause of IFI, other organisms (particularly moulds) have become increasingly prevalent. In particular, Aspergillus species are the leading cause of mould infections although other moulds including Fusarium species and Zygomycetes are increasing in frequency, and are associated with a high mortality rate. Options available for the prevention and treatment of these infections include standard and liposomal formulations of amphotericin B, but toxicity concerns limit their use; fluconazole is effective for the prevention and treatment of candidiasis but its inactivity against moulds and increasing resistance are limiting factors. Newer azoles, particularly voriconazole and posaconazole, have an enhanced spectrum of activity that includes Candida species, Aspergillus species, Cryptococcus species, dimorphic fungi, Fusarium species, and, for posaconazole, Zygomycetes. Recent data suggest that these agents are highly effective in a variety of clinical settings. Echinocandins have good activity against Candida species and Aspergillus species but their spectrum generally does not include Fusarium species, Cryptococcus species, Trichosporon species, Zygomycetes, and dematiaceous moulds. While these agents are unlikely to exhibit crossresistance with polyenes or azoles, they must be administered intravenously. Knowledge of the pathogenesis of IFIs and the activity, efficacy, and limitations of available treatment options will allow the selection of an appropriate antifungal agent for individual patients.